1. Field of the Invention
The present invention related to the concentration of aerosol particles and their collection for analysis. In particular, the invention is an air-to-air electrostatic aerosol concentrator that facilitates the collection of aerosol particles for analysis.
2. Description of Related Art
Existing integrated bioaerosol detection systems employ a two-step process in which microorganism-containing aerosol particles are collected and targets of interest are detected. Requirements for these two separate steps, however, are divergent and often conflicting. Most bio-analytical systems used for detection are based on liquid samples, and perform highly sensitive analysis on small sample volumes in the range of nanoliters to microliters, whereas bioaerosol samplers collect aerosols in liquid volumes of 1-10 ml or more. This difference between the sampling and sensing volumes can lead to false alarms, reduced sensitivity and increased logistical burden. While sample volumes may be reduced after bioaerosol collection, this adds significantly to the cost and complexity of the detection system. An improved aerosol concentration and collection system, which directly samples aerosol particles in small analysis volumes, is needed.
Conventional air-to-air aerosol concentration techniques are largely based on inertial mechanisms such as aerodynamic lenses, cyclones, and classical or virtual impactors. Use of these mechanisms, however, often includes high impaction losses in the flow modification region, low enrichment of particles, especially for particles <2 μm in diameter, low viability of microorganisms, and high cost of operation and manufacturing. Sample loss due to impingement in impactors can lead to poor detection sensitivity and high signal-to-noise ratios leading to false alarms. In addition, inertial systems lack flexibility and require significant redesign if specifications such as sampling parameters are altered.
Electrostatics-based concentration is an alternative to traditional inertial concentration technologies in which an externally applied electric field manipulates aerosol particles having native or induced charges into a smaller volume. Electrostatics-based concentration requires significantly less power than inertial systems and high-efficiency concentration and sampling can be achieved while maintaining the viability of biological aerosols. Furthermore, an electrostatic concentration method can be configured to distinguish between biological and non-biological particulates and operating conditions can be altered to select for particular particle fraction based on charge, size, and/or density, for example.
Current electrostatics-based technologies are typically directed toward the removal of particles from air or to augment inertial mechanisms. No existing devices use electrostatics to focus aerosol particles from an air stream into a smaller volume or to concentrate aerosol particles to form a high concentration aerosol.